Chemical nickel plating processes and baths therefor



United States Patent CHEMICAL NICKEL PLATING PROCESSES AND BATHS THEREFOR Gregoire Gutzeit, Highland, Ind, Paul Talmey, Earrington, 111., and Warren G. Lee, East Chicago, Ind, assignors to General American Transportation Corporation, Chicago, Ill., a corporation of New York No Drawing. Application March 3, 1955 Serial No. 492,032

8 Claims. (Cl. 11'713ll) The present invention relates to improved processes of chemical nickel plating of catalytic materials employing baths of the nickel cation-hypophosphite anion type and to improved baths therefor, and more particularly to such processes and baths involving a continuous system of the character of that disclosed in U. S. Patent No. 2,65 8,839, granted on November 10, 195 3 to Paul Talmey and William J. Crehan. This application is a continuation-in-part of the copending application of Gregoire Gutzeit, Paul Talmey and Warren G. Lee, Serial No. 376,968, filed August 27, 1953, now abandoned.

The chemical nickel plating of a catalytic material employing an aqueous bath of the nickel cation-hypophosphite anion type is based upon the catalytic reduction of nickel cations to metallic nickel and the corresponding oxidation of hypophosphite anions to phosphite anions with the evolution of hydrogen gas at the catalytic surface. The reactions take place when the body of catalytic material is immersed in the plating bath, and the exterior surface of the body of catalytic material is coated with nickel. The following elements are catalytic for the oxidation of hypophosphite anions and thus may be directly nickel plated: iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. The following elements are examples of materials which may be nickel plated by virtue of the initial displacement deposition of nickel thereon either directly or through a galvanic effect: copper, silver, gold, beryllium, germanium, aluminum, carbon, vanadium, molybdenum, tungsten, chromium, selenium, titanium and uranium. The following elements are examples of non-catalytic materials which ordinarily may not be nickel plated: bismuth, cadmium, tin, lead and Zinc. The activity of the catalytic materials varies considerably and the following elements are particularly good catalysts in the chemical nickel plating bath: iron, cobalt, nickel and palladium. The chemical nickel plating process is autocatalytic since both the original surface of the body being plated and the nickel metal that is deposited on the surface thereof are cata lytic; and the reduction of the nickel cations to metallic nickel in the plating bath proceeds until all of the nickel cations have been reduced to metallic nickel, in the presence of an excess of hypophosphite anions, or until all of the hypophosphite anions have been oxidized to phosphite ions, in the presence of an excess of nickel cations.

in a bath plating process, the reactions are sloweddown rather rapidly as time proceeds because the anions, as contrasted with the cations, of the nickel salt that is dissolved in the plating bath combine with the hydrogen cations to form an acid, which, in turn, lowers the pH of the bath, and the reducing power of the hypophosphite anions is decreased as the pH value of the bath decreases. Moreover, there is a tendency for the early formation in the plating bath of black precipitate that comprises a random chemical reduction of the nickel cations. Of course, this formation of the black precipitate comprises a decomposition of the plating bath, and is particularly objectionable in that it causes the nickel deposit to be coarse, rough and frequently porous. Any fine solid particles suspended in the plating bath, or adhering to the Walls of the plating vessel, at the plating temperature,

2,819,187 Patented Jan. 7, 1958 initiate the formation of the black precipitate by acting as nuclei.

In a continuous plating process, the reactions are maintained substantially at their initial rates by the regeneration of the plating bath, i. e., by the adding thereto of soluble nickel-containing and hypophosphite-containing reagents, as well as an alkali for pH control; however, the problem of preventing the formation of black precipitate in the plating bath and the consequent decomposition thereof is the same as that previously mentioned. Moreover, another practical difficulty is encountered in the continuous plating process that is not encountered in the bath plating process in that there is a considerable buildup of the by-product phosphite therein as time proceeds and as a consequence of the cycling of the bath. More particularly, while nickel hypophosphite is readily soluble in an aqueous solution, nickel phosphite is much less soluble in an aqueous solution, whereby there is a tendency, as the phosphite concentration of the plating bath builds up, for nickel phosphite to be precipitated therein, and thereby provide the solid particles that serve as nuclei for the formation of the black precipitate therein, previously mentioned. in passing, it is noted that the initiation of the precipitation of nickel phosphite in the plating bath is indicated by turbidity thereof.

In carrying out the chemical nickel plating process on a commercial scale, the continuous system disclosed in the T almey and Crehan patent mentioned may be employed; which system involves periodic or continuous regeneration of the plating bath by the addition thereto of appropriate ingredients for the purpose of maintaining substantially constant the composition of the bath as previously noted. More specifically in this system, there are provided a plating chamber and a reservoir; preferably one portion of the plating solution is stored at a relatively low temperature well below the boiling point thereof in the reservoir; and preferably another portion of the plating solution is held as a bath at a relatively high temperature slightly below the boiling point thereof in the plating chamber. The solution is continuously circulated at a low rate from the reservoir to the plating chamber and then back to the reservoir, the solution being heated substantially to the relatively high temperature after withdrawal thereof from the reservoir and before introduction thereof into the plating chamber, and the solution being cooled substantially to the relatively low temperature after withdrawal thereof from the plating chamber and before return thereof to the reservoir. The body that is to be nickel plated is immersed in the bath in the plating chamber and is subsequently withdrawn from the bath in the plating chamber after a time interval corresponding to the thickness of the nickel plating thereon that is desired; and during such time interval soluble reagents are added to the solution in the reservoir to maintain in the bath in the plating chamber during such time interval substantially the predetermined composition of the bath previously mentioned, so as to compensate for the ingredients of the bath that are exhausted during the time interval in the plating chamber. This regeneration of the solution in the reservoir consists essentially of adding thereto appropriate amounts of soluble nickel-containing and hypophosphite-containing reagents, as well as an alkali for pH control, as previously noted.

A typical chemical nickel plating bath that may be employed in the continuous plating process of the Talmey and Crehan patent is disclosed in U. S. Patent No. 2,658,- 841, granted on November 10, 1953, to Gregoire Gutseit and Abraham Krieg; which plating bath essentially comprises an aqueous acid solution of a nickel salt and a hypophosphite and a buffer in the form of an alkaline acetate; the pH of the bath being within the approximate range 4.5 to 5.6, the absolute concentration of hypo phosph'ite ions in the bath being in the range 0.15 to 0.35 mole/liter, the ratio between nickel ions and hypophosphite ions in the bath being in the range 0.25 to 0.60, and the absolute concentration of acetate ions in the bath being approximately 0.120 mole/liter.

In carrying out of the chemical nickel plating process on a commercial scale employing the continuous system of Talniey and Crehan, it has been discovered that the chemical nickel plating bath of Gutzeit and Krieg is not altogether satisfactory in that the bath does not have as fast a plating rate as is desirable; and moreover, the bath is most effective within a relatively narrow pH range. Furthermore, nickel phosphite begins to precipitate at a phosphite ion concentration of about 0.07 mole/liter so that the stability of the bath is not that desired, and the useful life thereof is entirely too short.

The present invention is predicated upon the discovery that plating baths of the nickel cation-hypophosphite anion type mentioned may have their stable life increased, the plating rates thereof may be substantially increased, the useful life thereof may be greatly extended, and the activity thereof with regard to the usable pH range may be greatly broadened by the addition thereto of both a complexing agent substantially completely complexing all of the nickel ions in the plating bath, and an exalting additive substantially exalting the plating rate of the plating bath. The complexing agent is selected from the group consisting of ammonium compounds; and the exalting additive is selected from the group consisting of simple short chain saturated aliphatic mo-nocarboxylic acids including 3 to 5 carbon atoms and salts thereof, simple short chain saturated aliphatic dicarboxylic acids including 3 to 6 carbon atoms and salts thereof, and short chain aliphatic aminocarboxylic acids and salts thereof.

More particularly, the plating baths of the present invention have an increased stable life in that the ability thereof to hold nickel phosphite in solution at high phos phite concentration is enhanced as evidenced by the clarity of the bath (the lack of turbidity thereof). Also, these plating baths have a nickel plating rate of at least l mil/hour (0.00l"/hour), or expressed in c. g. s. units, of at least 3.5 l0 gm./cm. /min. Moreover, these plating baths have an activity within a broad pH range (4.0 to 11.0); and no precipitation of nickel phosphite takes place therein even at a phosphite ion concentration in some cases as high as 1.0 mole/liter. Further, the plating appearance on both metals and non-metals is excellent (bright, smooth and non-porous); and the adhesion of the nickel plating on both metallic and nonmetallic bodies is satisfactory over the pH range mentioned, and is particularly good in the acid range (no substantial flaking of the nickel coating in bending, abrading and shock tests).

The ammonium ions form various molecular complexes with the nickel ions depending upon the molar ratio therebetween in the plating bath. The diammino complex (lowest coordination number) is formed when the molar ratio between the ammonium ions and the nickel ions is 2; the tetraarnino complex (intermediate coordination number) is formed when the molar ratio between the ammonium ions and the nickel ions is 4; and the hexammino complex (highest coordination number) is formed when the molar ratio between the ammonium ions and the nickel ions is 6. Thus, in order to complex at least 100% of nickel ions, the molar ratio between the ammonium ions and the nickel ions should be at least 2.

The organic ions of the exalting additive in the plating bath effect a substantial increase in the plating rate thereof; and the required absolute concentration of the various ones of the organic ions is somewhat variable, but is generally within the range 0.4 to 0.10 mole/liter depending upon the particular one of the exalting additives employed in the plating bath, as illustrated in the typical plating baths appearing hereinafter.

Furthermore, in the plating bath, the ratio between nickel ions and hypophosphite ions is Within the approximate range 0.25 to 1.60, the absolute concentration of hypophosphite ions is within the approximate range 0.15 to 1.20 mole/liter, the absolute concentration of ammo nium ions is sufiicient to complex at least 100% of the nickel ions as the diammino complex (lowest coordination number) and the absolute concentration of the exalting ions is at least about 0.04 mole/liter. The pH of the bath may be in the approximate range 4.0 to 11.0 but is preferably in the range 5.0 to 7.0.

The terms cations, anion and ion as employed herein, except where specifically noted, include the total quantity of the corresponding element that is present in the plating bath; i. e., both undissociated and dissociated material. In other words, 100% dissociation is assumed when the terms noted are used in connection with molar ratios and concentrations in the plating bath.

in accordance with the process of the present invention, the ammonium compound, if added in suflicient quantity, substantially completely complexes all of the nickel ions in the plating bath, whereby it ties-up" the nickel cations almost completely releasing only a small fraction thereof depending on the complex stability constant (dissociation constant of the complex ion); whereas the exaltant increases the plating rate of the plating bath. Thus, it will be understood that the plating bath, except for the exaltant, would have an exceedin ly low plating rate due to the tying-up of the nickel cations therein. However, this tying-up of the nickel cations in the plating bath is the fundamental factor contributing to the clarity of the solution, preventing the formation of precipitated phosphites therein, and giving the bath an exceedingly long life in spite of the build-up of phosphite ions therein to a concentration even in excess of one molar. Of course, the complex of nickel in the plating bath is watersoluble and of medium stability resulting in a bond strong enough to prevent the nickel cations from forming insoluble nickel compounds, such as the phosphite, the succinate, the malonate, etc., and mixed basic salts thereof, as explained more fully hereinafter, but having a stability constant low enough to release the nickel cations required for the nickel plating operation and permitting the exalting additive to bring about a plating rate of the bath of at least 3.5)(10- gm./cm. /min., as previously explained.

in the plating bath the nickel ions may be derived from any suitable nickel salt (nickel chloride, nickel sulfate, nickel hypophosphite, etc.); the hypophosphitc ions may be derived from any suitable hypophosphite (sodium hypophosphite, nickel hypophosphite, etc); and the ammonium ions may be derived from any suitable ammonium compound (ammonium hydroxide, ammonium chloride, ammonium sulfate, etc). In the continuous plating system of T almey and Crehan, the plating bath is utilized in the plating chamber at a temperature slightly below the boiling point thereof (and above C.), ordinarily at about 97-99 C.

in view of the foregoing, it is the primary object of the present invention to provide an improved nickel plating pracess of the character described in which the reactions involved carried out more efficiently and under more stable conditions (clarity of solution) than heretofore, thereby rendering the process more desirable from a commercial standpoint.

Another object of the invention is to provide an improved aqueous chemieal nickel plating bath that may be employed with advantage in the practice of the improved process.

Another object of the invention is to provide an improved nickel plating process of the character described, that employs a plating bath of the nickel cation-hypo phosphite anion type containing both an ammonium com- 5 pounds and an exaltant, wherein the ammonium compound substantially completely complexes all of the nickel cations in the bath, and the exaltant substantially increases the plating rate of the bath obtaining a plating rate thereof of at least 3.5 lgm./cm. /min.

A further object of the invention is to provide an improved nickel plating process of the continuous type involving an improved plating bath of the nickel cationhypophosphite anion type so that the useful life thereof is greatly extended in that the plating bath remains clear notwithstanding the presence therein of a phosphite anion concentration as high as one molar.

A still further object of the invention is to provide an improved nickel plating bath of the character described that incorporates a novel combination of an ammonium compound and an exaltant.

These and other objects and advantages of the invention pertain to the particular arrangement of the steps of the process and of the composition of the plating bath, as will be understood from the foregoing and following description.

In accordance with the process of the present invention, the article to be nickel plated and normally having a catalytic surface is properly prepared by mechanical cleaning, degreasing and light pickling substantially in accordance with standard practices in electroplating processes. For example, in the nickel plating of a steel object, it is customary to clean the rust and mill scale from the object, to degrease the object, and then lightly to pickle the object in a suitable acid, such as hydrochloric acid. The object is then immersed in a suitable volume of the bath containing the proper proportions of nickel cations, hypophosphite anions, an ammonium compound and an exaltant, the pH of the bath having been, if necessary, adjusted to an optimum value by the addition of an appropriate acid or base, and the bath having been heated to a temperature just below its boiling point, such as 99 C., at atmospheric pressure. Almost immediately hydrogen bubbles are formed on the catalytic surface of the steel object and escape in a steady stream from the bath while the surface of the steel object is slowly coated with metallic nickel (containing some phosphorus). The steel object is ultimately removed from the bath after an appropriate time interval corresponding to the required thickness of the nickel coating deposited thereon that is desired. Ultimately the steel object is rinsed oif with water, and is then ready for use.

Typical plating baths embodying the present invention and composed from various ammonium compounds are as follows:

Nickel chloride (in. p. l.) Sodium hypophosphite (m. p. l.) Ammonium hydroxide (in. p. l. Ammonium chloride (in. p. l.)...- Ammonium sulfate (in. p. l.) Propionic ion (m. p. l.). pH

Typical plating baths embodying the present invention and including various simple short chain saturated aliphatic monocarboxylic acids including 3 to 5 carbon 6 Typical plating baths embodying the present invention and including various simple short chain saturated aliphatic dicarboxylic acids including 3 to 6 carbon atoms, or salts thereof, are as follows:

Bath Bath Bath Bath No. 7 No.8 No. 9 No. 10

Nickel sulfate (m. p. l.) 0. 0675 Sodium hypophosphite (m. p. 1.) Ammonium sulfate (in. p. 1.) Malonic ion (in. p. Succinie ion (in. p. Glutarie ion (m. p. Adipic ion (m. p. 1 pH Typical plating baths embodying the present invention and including various short chain aliphatic aminocarboxylic acids, or salts thereof, are as follows:

Bath Bath Bath No. 11 No. 12 No. 13

Nickel sulfate (m. p. l.) 0. 0675 0. 0675 O. 0675 Sodium hypophosphite (m. p 0.225 0.225 0.225 Ammonium sulfate (in. p. 1.). 0. 068 0.068 0. 068 Aminoacetic ion (m. p. l.) 0.1 Alpha-amiuopropionic ion (m. p. l.) 0. 1 Beta-ammopropio'nic ion (m. p. l.).. O. 1 pI-I 5. 0 5. 0 5. 0

Bath Bath Bath No. 14 No. 15 No. 16

Nickel sulfate (m. p. l.) 0. 0675 Sodium hypophosphite (m. p. l. 0. 225 Ammonium sulfate (m. p. 1.). 0.068 0. 068 0. 068 Alpha-amiuobutyrio ion (m. p.-l.) 0.1 Aminosuccinic ion (m. p. l.) 0106 Ethylenediaminotetraacetic ion (in. p. l.) 0. 04 pH 5.0 5.0 5.0

In plating baths No. 1 to No. 16, inclusive, the required organic ions (the exalting additives) may be introduced by the addition of either the corresponding organic acids or the salts thereof, such as the alkali metal salts of these organic acids. Moreover, in these plating baths the content of ammonium ions (the complexing agent) is not particularly critical, provided there are suflicient ammonium ions to complex at least about of the nickel cations present to nickel diammine; whereby a minimum of 0.135 m. p. l. of ammonium hydroxide or ammonium chloride and a minimum of 0.0675 m. p. l. of ammonium sulfate are required to complex 0.0675 m. p. 1. of nickel cations to nickel diammine. Thus, in plating baths No. 1 to No. 16, inclusive, the minimum amounts of ammonium compounds have been set forth, it being understood that the maximum amounts thereof are three times the minimum amounts set forth; which maximum amounts of ammonium compounds eifect complexing of the nickel cations to nickel hexammine. As a matter of convenience, these plating baths may be initially composed containing about of the stoichiometric amount of ammonium ions to achieve complete complexing of the nickel cations present, as there is some loss of the ammonium ions as time proceeds through the boiling-ofiof ammonia. Accordingly, in the regeneration of these plating baths, it is also necessary to supply the required ammonium ions, as required; and it is recommended that ammonium hydroxide be employed in this regeneration, since it not only provides the required ammonium ions for complexing the nickel cations, but it also provides at least some of the hydroxyl ions that are required for pH control, as previously explained. Thus, it may be found convenient to employ in the regeneration of these plating baths a combination of ammonium hydroxide and sodium hydroxide to achieve the required additions of both ammonium ions and hydroxyl ions.

In these plating baths, it is believed that the phenomenon of exaltation results from the formation of heteropoly-aci-ds between the organic additive and the hypophosphite anionswhich compete with the nickel complex formation. The composite complexing effect and exalting effect in a plating bath of this type may be readily established by a series of plating tests employing appropriate variations of the ingredients thereof. As an illustration of this procedure, a typical aqueous plating bath was prepared that contained no exaltant and had 8 from the group consisting of ammonium compounds supplying NH ions to said bath, the molar ratio between the NH ions and the nickel ions in said bath being in the range 2 to 6 so as substantially completely to complex all of the nickel ions in said bath; said additive being present in said bath in an amount sufficient substantially to exalt the normal plating rate of said bath and being selected from the group consisting of simple short chain saturated aliphatic monocarboxylic acids includthe following composition: ing 3 to 5 carbon atoms and salts thereof, simple short Bath A chain saturated aliphatic dicarboxylic acids including to 6 carbon atoms and salts thereof, and short chain ali- Nickel chloride m. p. 1.. 0.0675 phatic aminocarboxylic acids and salts thereof; wherein Sodium hypophosphite m. p. l 0.225 the absolute concentration of hypophosphite ions in said Ammonium hydroxide m. p. l 0.135 bath expressed in mole/liter is within the range 0.15 to Stabilizing ion Pb++ p. p. m 1.0 1.20, the ratio between nickel ions and hypophosphite pH adjusted with HCl. ions in said bath expressed in molar concentrations is In plating bath A, the Pb++ comprises a stabilizing g i igi fg and a g g of said ion as disclosed in the copending application of Paul 20 sla g g i to ickel a Talmey and Gregoire Gutzeit, Serial No. 359,428, filed b e g f 0 R p t d ,3 th June 3, 1953, now Patent No. 2,762,723, granted Septem- 0 y Essen conpnsmg 1 0 23 T om 6 ber 11, 1956: this stabilizing ion is present in only the group i ii 0 E 2. 00 a i i a trace amount of one part per 1,000,000 parts of the bath SI "9 3 8 mm i p annum Comby Weight and is not related either to the complexing i i P Said body Wit .aqueous at eiieot or to the exalting effect comprising the present ina pnsmg mckel hypoifliosphlie long a Pomplexmg vcntiom agent, and an exalting add1t1ve; said agent being selected Toplating bath A, increased amounts of sodium sucm the group consisting of ammonium compfmnds cinate were added from 0 to 0.09 m. p. l. and correspondplying ions to Said bath, the f IatlO a 0 ing plating tests were performed on properly cleaned steel the ions and the nickel ions In 5314 hath 36mg 111 samples of 20 cm. area for 10 minutes and 60 minutes, the range 2 to 6 so as substantially completely to comthe volume of the bath being 50 cc. and the temperature plex all of the nickel ions in said bath; said additive bethereof being about 99 C., with the following results: ing present in said bath in an amount sutficient substan- Succinate, m. p. l. none 0.03 0.06 0.09

Plating time. 10 60 10 10 60 10 63 Initin1pH 5. 01 5.01 5.00 5.51 s. 00 5.51 5.03 5.00 Wt. gain..- 0. 0500 0.1 0. 0s04 0. 0971 0.1500 0.1788 0.1033 0. 2010 Plating rate, RX10 0. 00 2. s3 4.02 4.86 5.10 Turbidity none none none none none none none none none none From the above, it will be observed that the plating tially to exalt the normal plating rate of said bath and rate of bath A at a pH of 5.00 with 0.09 m. p. l. of sucbeing selected from the group consisting of simple short cinate ion is very high (over 1.4 mils/hour). chain saturated aliphatic monocarboxylic acids including in view of the foregoing, it is apparent that there has 3 to 5 carbon atoms and salts thereof wherein the absobeen provided an improved process of chemical nickel lute concentration of hypophosphite ions in said bath plating, as well as improved plating baths therefor, whereexpressed in mole/liter is within the range 0.15 to 1.20, in the baths are of the nickel cation-hypophosphite type, the ratio between nickel ions and hypophosphite ions in also containing an ammonium compound substantially said bath expressed in molar concentrations is within the completely complexing all of the nickel ions in the bath, range 0.25 to 1.60, and the initial pH of said bath is and also containing an exaltant substantially exalting the Within the approximate range 4.0 to 11.0. plating rate of: the bath and being selected from the group 3. I The process of chemically plating with nickel a body consisting of simple short chain saturated aliphatic aminoessentially comprising an element selected from the group carboxylic acids including 3 to 5 carbon atoms and salts consisting of iron, cobalt, nickel, aluminum, copper, silthercof, simple short chain saturated aliphatic dicarboxylic ver, gold, palladium and platinum, which comprises conacids including 3 to 6 carbon atoms and salts thereof, tacting said body Wi an aqueous hath comprising nickel and short chain aliphatic aminocarboxylic acids and salts ions, hypophosphite ions, a complexing agent, and an thereof. The plating baths are particularly well-adapted exalting additive; said agent being selected from th for use in a continuous plating system as they exhibit a group consisting of ammonium compounds supplying fast plating rate, have a long life, and maintain nickel iOIIS Said bath, the molar ratio hetweah the phosphite in solution in concentrations as high as onev 0 NH ions and the nickel ions in said bath being in the molar. range 2 to 6 so as substantially completely to complex While there has been described what is at present all of the nickel ions in said bath; said additive being sidered to he the preferred embodiment of the invention, Present in Said bath in an 11111011111 Sufficient Substantially it will be understood that various modifications may be $0 eXalt the normal P g fate of Said bath and being made therein, and it is intended to cover in the appended 65 Selected from the group Consisting of Simple short Chain claims all such modifications as fall within the true spirit Saturated aliphatic dical'boxyhc acids including 3 t0 6 and scope of the invention. carbon atoms and salts thereof; wherein the absolute What is claimed is: concentration of hypophosphite ions in said bath exl. The process of chemically plating with Ilickgl a pressed in mole/liter is within the range 0.15 to 1.20, body essentially comprising an element selected from the ratio betwefih nickel ions and YP P P ions in the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath comprising nickel ions, hypophosphite ions, a complexing agent, and an exalting additive; said agent being selected said bath expressed in molar concentrations is within the range 0.25 to 1.60, and the initial pH of said bath is within the approximate range 4.0 to 11.0.

4. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath comprising nickel ions, hypophosphite ions, a complexing agent, and an exalting additive; said agent being selected from the group consisting of ammonium compounds supplying NH ions to said bath, the molar ratio between the NH ions and the nickel ions in said bath being in the range 2 to 6 so as substantially completely to complex all of the nickel ions in said bath; said additive being present in said bath in an amount sufficient substantially to exalt the normal plating rate of said bath and being selected from the group consisting of short chain aliphatic aminocarboxylic acids and salts thereof; wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the ratio between nickel ions and hypophosphite ions in said bath expressed in molar concentrations is within the range 0.25 to 1.60, and the initial pH of said bath is within the approximate range 4.0 to 11.0.

5. The process of chemically plating with nickel a body essentially comprising an element selected from the group consisting of iron, cobalt, nickel, aluminum, copper, silver, gold, palladium and platinum, which comprises contacting said body with an aqueous bath comprising nickel ions, hypophosphite ions, a complexing agent, and an exalting additive; said agent being selected from the group consisting of ammonium compounds supplying NH ions to said bath, the molar ratio between the NH ions and the nickel ions in said bath being in the range 2 to 6 so as substantially completely to complex all of the nickel ions in said bath; said additive being present in said bath in an amount sufiicient substantially to exalt the normal plating rate of said bath and consisting essentially of succinic acid and salts thereof; wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the ratio between nickel ions and hypophosphite ions in said bath expressed in molar concentrations is within the range 0.25 to 1.60, and the initial pH of said bath is within the approximate range 4.0 to 11.0.

6. A bath for the chemical plating of a catalytic material with nickel comprising an aqueous solution of a nickel salt, a hypophosphite, a complexing agent and an exalting additive; said agent being selected from the group consisting of ammonium compounds supplying NH ions to said bath, the molar ratio between the NH ions and the nickel ions in said bath being in the range 2 to 6 so as substantially completely to complex all of the nickel ions in said bath; said additive being present in said bath in an amount suflicient substantially to exalt the normal plating rate of said bath and being selected from the group consisting of simple short chain saturated aliphatic monocarboxylic acids including 3 to 5 carbon atoms and salts thereof, simple short chain saturated aliphatic dicarboxylic acids including 3 to 6 carbon atoms and salts thereof, and short chain aliphatic aminocarboxylic acids and salts thereof; wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the ratio between nickel ions and hypophosphite ions in said bath expressed in molar concentrations is within the range 0.25 to 1.60, and the iniital pH of said bath is within the approximate range 4.0 to 11.0.

7. A bath for the chemical plating of a catalytic material with nickel comprising an aqueous solution of a nickel salt, a hypophosphite, a complexing agent and an exalting additive; said agent being selected from the group consisting of ammonium compounds supplying NH ions to said bath, the molar ratio between the NH ions and the nickel ions in said bath being in the range 2 to 6 so as substantially completely to complex all of the nickel ions in said bath; said additive being present in said bath in an amount sufficient substantially to exalt the normal plating rate of said bath and being selected from the group consisting of simple short chain saturated aliphatic dicarboxylic acids including 3 to 6 carbon atoms and salts thereof; wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the ratio between nickel ions and hypophosphite ions in said bath expressed in molar concentrations is within the range 0.25 to 1.60, and the initial pH of said bath is within the approximate range 4.0 to 11.0.

8. A bath for the chemical plating of a catalytic material with nickel comprising an aqueous solution of a nickel salt, a hypophosphite, a complexing agent and an exalting additive; said agent being selected from the group consisting of ammonium compounds supplying NH ions to said bath, the molar ratio between the NH ions and the nickel ions in said bath being in the range 2 to 6 so as substantially completely to complex all of the nickel ions in said bath; said additive being present in said bath in an amount sulficient substantially to exalt the normal plating rate of said bath and consisting essentially of succinic acid and salts thereof; wherein the absolute concentration of hypophosphite ions in said bath expressed in mole/liter is within the range 0.15 to 1.20, the ratio between nickel ions and hypophosphite ions in said bath expressed in molar concentrations is within the range 0.25 to 1.60, and the initial pH of said bath is within the approximate range 4.0 to 11.0.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE PROCESS OF CHEMICALLY PLATING WITH NICKEL A BODY ESSENTIALLY COMPRISING AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF IRON, COBALT, NICKEL, ALUMINUM, COPPER, SILVER, GOLD, PALLADIUM AND PLATINUM, WHICH COMPRISES CONTACTING SAID BODY WITH AN AQUEOUS BATH COMPRISING NICKEL IONS, HYPOPHOSPHITE IONS, A COMPLEXING AGENT, AND AN EXALTING ADDITIVE; SAID AGENT BEING SELECTED FROM THE GROUP CONSISTING OF AMMONIUM COMPOUNDS SUPPLYING NH4+ IONS TO SAID BATH, THE MOLAR RATIO BETWEEN THE NH4+ IONS AND THE NICKEL IONS IN SAID BATH BEING IN THE RANGE 2 TO 6 SO AS SUBSTANTIALLY COMPLETELY TO COMPLEX ALL OF THE NICKEL IONS IN SAID BATH; SAID ADDITIVE BEING PRESENT IN SAID BATH IN AN AMOUNT SUFFICIENT SUBSTANTIALLY TO EXALT THE NORMAL PLATING RATE OF SAID BATH AND BEING SELECTED FROM THE GROUP CONSISTING OF SIMPLE SHORT CHAIN SATURATED ALIPHATIC MONOCARBOXYLIC ACIDS, INCLUDING 3 TO 5 CARBON ATOMS AND SALTS THEREOF, SIMPLE SHORT CHAIN SATURATED ALIPHATIC DICARBOXYLIC ACIDS INCLUDING 3 TO 6 CARBON ATOMS AND SALTS THEREOF, AND SHORT CHAIN ALIPHATIC AMINOCARBOXYLIC ACIDS AND SALTS THEREOF; WHEREIN THE ABSOLUTE CONCENTRATION OF HYPOHOSPHITE IONS IN SAID BATH EXPRESSED IN MOLE/LITER IS WITHIN THE RANGE 0.15 TO 1.20, THE RATIO BETWEEN NICKEL IONS AND HYPOPHOSPHITE IONS IN SAID BATH EXPRESSED IN MOLAR CONCENTRATIONS IS WITHIN THE RANGE 0.25 TO 1.60, AND THE INITIAL PH OF SAID BATH IS WITHIN THE APPROXIMATE RANGE 4.0 TO 11.0. 